function M_cell = file_fetch(file_name,sheet_name)  %read the file to a set, return a cell_structure ,and each cell store a track's msg
M = xlsread(file_name,sheet_name)'; % read file to a set, 3 line a music track
M(isnan(M)) = 0; 
[line,~] = size(M);  % get the line number of M
for i=1:line/3  
    M_cell{i} = M((i-1)*3+1:i*3,:); % to store diff track to diff cell
    M_cell{i}(1,find(M_cell{i}(1,:)==0))=8;  % for rest special 
end

end

